The field of the invention is the preparation of ammonia and hydrogen chloride from ammonium chloride.
Ammonium chloride is obtained as a byproduct in a series of industrial processes, mostly as an aqueous solution. This applies for instance to the Solvay process for making sodium carbonate, to the preparation of phosphoric acid by the process of British Pat. No. 1 541 538 and for all other methods in which hydrochloric acid is neutralized with ammonia or ammonia with hydrochloric acid.
The state of the art of making ammonium chloride may be ascertained by reference to the Kirk-Othmer, Encyclopedia of Chemical Technology, 2nd Edition, Vol. 2 (1963), pp. 316-319 under the section entitled "Ammonium Chloride"; U.S. Pat. No. 3,443,889; British Pat. No. 1,541,538; and Israeli Pat. No. 33,552, the disclosures of which are incorporated herein.
The disclosure of U.S. Pat. No. 4,115,530 is also incorporated herein to amplify one of the steps of the present invention.
According to the state of the art, ammonium chloride is prepared as the substance itself, or it is treated with a suitable alkalinically reacting material such as sodium carbonate liquor or lime solution for the purpose of recovering the ammonia. Now there is little application for ammonium chloride, since it has only little significance as a fertilizer, and the reaction with for instance NaOH or Ca(OH).sub.2 results in losing both the alkali or earth-alkali ion and the chloride ion, since the chlorides produced in addition to the ammonia as a rule are not utilized, rather they are fed as waste liquors to the sewer and therefore cause substantial ecological damage.